Take a look at the attached dynos.

http://web.tampabay.rr.com/maxgator/oldVSrecent.BMP

Run 1 is my original all stock (with a big blip at rev limiter), the other is all stock today.

Original stock = 197 (really only about 193)
Current stock = 163.7

In fact, there's about a 40 hp loss at red-line and peak hp has moved from redline all the way back to 5k.

I won't go into all the problems I'm having with getting Nissan to diagnose the problem. Suffice it to say, I think getting them to admit there is a problem will win the war.

What I'm trying to figure out is - what's causing the problem. The dyno graph almost looks like it is a 4th gen.

It sure seems like the problem is in the variable intake (VIAS system), since the curves follow all the way up to intake switchover, but once the switchover happens, there is no power increase.

After much prodding (2days worth) They've done the VIAS diagnostic and everything checks out. I figured it would since you can visually watch the actuator flip when the car hits 5k rpms.

Anyone else have this problem?
Any suggestions on what it might be?


Thanks.

John.

 

Clogged fuel filter?
Dirty air filter?
Worn spark plugs?
Bad ignition coils?

But it sure does look like the VIAS is not switching... Maybe the actuaitor is moving but the valve is some how not fully opening?

 

That's what several have speculated - somehow the valve isn't functioning correctly.

Fuel filter is supposedly maint. free; air filter is fine

Plugs and coils are both possibilities.

Of course, Nissan won't accept my dyno as proof of the power loss. We are going to do a comparo with another 5th gen 5spd. If they don't agree after that - KABOOM (and I don't mean the engine).

 

MardiGras -

From your other post, it seems you have a good understanding of the mechanics of the VIAS.

Are there any diagrams or tech writeup anywhere of how it works so that I might be able to point the idiots in that direction??

 

Just the factory service manual...

I have a thought. The actuator needs vacuum to pull the valve open. At idle and part throttle you have good vacuum all the time. At wide open throttle the actuator gets vacuum from a vacuum tank. This tank has to have a vacuum check valve between it and its manifold vaccum source so it will hold the vacuum when you go to wide open throttle. If the vacuum tank has a leak or the vacuum check valve wont hold the vacuum it wont open at wide open throttle, but it will open at part throttle at 5k when there is still a bit of manifold vacuum. You could test this by running the car for a minute, then cutting it off, them pulling the vacuum hose that feeds vacuum to the VIAS control switch. If you hear air rush in as you pull the hose off, the tank and the check valve are good, if you dont they are faulty.

Or you can put it back on the dyno and look at the valve to see if it pulls open at WOT?

 

If I recall correctly, the tech said the valve didn't open, but rather closed at 5k when operating properly. But I'm not sure what he knows - he didn't have any clue what I was talking about when I referred to VIAS until he read the FSM.

I'll have to look more closely at the assembly since I really don't know what does what (that's why the request for a diagram).

I'll look for the vacuum hose and test that out.

thanks!

 

Without a doubt the issue is the intake manifold not switching over. That dyno plot past 5000 is for all intents and purposes identical to a 4th gen plot.

Check the solenoid valve for the vacuum line that routes to the manifold. Check the actuator valve itself at the manifold. There's not a whole lot else to the system. Check the vacuum lines also for cracks, disconnects, or plugged lines. Is there any way to mark the actuator valve with a paint mark to see if it's indeed actuating or not? Sorry if that's not possible...I'm not positive whether or not that can be done on the 5th gen.

 

The actuator valve flips when 5000 rpms is hit.

I've watched it on the dyno.

Dealer has done the VIAS diagnostic which confirms that the actuator is working and that there is power.

I think there's something going on inside.

Believe it or not - I'm still fighting with the dealer OVER WHETHER THERE IS ANYTHING WRONG - AND I SHOWED THEM THE DYNO!!! They want to "test" it against another car by the seat of their pants - idiots.

 

Ahhhhh yes the old Dyno-Butt 2000, thats so acurate!

 

$750 into a $7000 value'd car = stupid

I finally came to that realization.

I'm all over the concept of the intake manifold and drool at the possibility of having it on my car, but I have some common sense. There's no way I can justify that much money.

 

Thats just over 10%, many who s/c spend well over that ratio to their vehicles value. I have a 98 I30t 5spd that I bought for $11,000 and I can't wait to spend $2500 on a s/c. To each is their own.

 

more detailed thread at:

http://forums.maxima.org/showthread.php?threadid=99861

FINALLY!

Nissan has agreed to replace my variable intake. The caveat is that they will not do it under warranty . . . but they are doing it as customer goodwill. If that does not solve the problem - I give.

I will say that the service manager - Terry - has been very cooperative in helping me get this done. In short, I think he believed that I had a problem but did not want to confirm it because he could not determine what the problem was and didn't want Nissan to be stuck with it. Although I'm not pleased with that type of behavior in general, I'm pretty certain his hands were tied in that regard by Nissan.

Interestingly, I believe it was ultimately the fact that I let him know that I was seriously considering making a lemon law claim or breach of warranty claim, that may have given him a basis to get this done.

Overall, I really am not happy that I have had to work this hard to diagnose the problem and force them to fix it. And I am not happy that it has taken them this long to do it under goodwill. Unfortunately, it appears to be the result of an uncommon problem, lack of information about how their own cars work, and a bureaucratic system that makes it impossible to communicate with the people who can make the diagnosis.

I hope to attend the repair and if I ever figure out EXACTLY what is wrong, I will let everyone know. Looks like sometime next week since they have to order the variable intake.

 

see if they will give you the old variable intake off the car, if u can get it i want it
-pete

 

Update here:

http://forums.maxima.org/showthread.php?threadid=113198